‘Ring by Spring”: That’s what they say at religious colleges across the country. As the snow starts to melt and the pollen counts begin to rise, the number of students getting engaged starts to soar. From Brigham Young University to Notre Dame, young people realize that their senior year of college may be the last time they’re around such a large pool of their co-religionists, and some decide it’s time to make a commitment.

These young people are, of course, unlike those on other campuses. Much more typical is Jessica Salley, a Harvard senior, who writes in the university’s magazine that she and her friends see “having children, and even marriage [as] entirely abstract ideas at this point.”

And when she finds that people she knew in high school are already reproducing, she exclaims, “My old classmates who are having children now are no longer just products of bad sex education. . . They think they can have stable relationships and children at 21 and 22, before they have a degree or a job.”

This is a common refrain these days, that marrying early leads to unstable relationships. But that’s only true up until the mid-20s or so. After that, it turns out, men and women usually have a pretty good foundation for a marriage. But for the educated classes, even the idea of marriage by 25 seems backward.

Which is one reason why there’s so much backlash at “Marry Smart,” a new book by Susan Patton, a Princeton grad and the mother of two sons who also graduated from her alma mater.

Patton advises women to start considering marriage much earlier. She warns that, just like those young people at religious schools, co-eds will see the potential marriage pool starting to shrink a few minutes after those mortarboards are thrown in the air.

But it’s not co-religionists she’s worried about. It’s women having a chance to find their intellectual equals. “Honestly,” she asks, “where do you think you will find super-smart men once you are no longer a student? At a bar? Online? Once you enter the real world, you’ll be stunned by how smart the men are . . . not.”

Indeed, she warns women that if you associate “too closely with a man who is significantly below your intellectual level, you will eventually get stupid juice all over you.”

To which there is no response except . . . Ewwww.

Patton’s advice to start thinking about marriage and family before you turn 29 is sensible enough, but there’s not much evidence to back up her theory that if you don’t find a mate in college or soon after you’ll be forced to marry a dolt.

In fact, Americans now are very much into what’s called “assortative mating”: Both men and women tend to marry within their socioeconomic class.

Bosses aren’t marrying their secretaries. Henry Higgins doesn’t go for Eliza Doolittle; “Maid in Manhattan” is even more of a fairy tale than you think. (A recent study even suggested that the rise in US income inequality is largely driven by the fact that all the smart, successful people are marrying each other.)

Christine Whelan, a professor of sociology at the University of Wisconsin, notes that “there are plenty of opportunities after college — in graduate school, through friends and at work — to meet and marry a kind, supportive and smart person.”

For her book “Why Smart Men Marry Smart Women,” Whelan analyzed Census data to find that (contrary to Patton’s anecdotal evidence) educated men may be just as embarrassed to have a bimbo on their arms as women are to have a “himbo.”

And since everyone is marrying later, there may not be as much of a “pool” problem for women as the media likes to claim. Certainly not for the Ivy League women that are Patton’s focus: Whelan’s research says that a 30-year-old woman with a graduate degree or above, or a woman earning in the top 10 percent of income for her age range, has a 75 percent chance of tying the knot in the next 10 years.

Patton is right that younger women would be smarter to think about husbands and children, not just high-powered careers. And there is no doubt that women’s biological clocks are ticking much faster than men’s.

But if they don’t get a ring by spring, chances are they’ll still find Mr. Smarty Pants.